The lawyers at AZ have been all over the contracts with a fine tooth comb, and so have the EU lawyers! I think it is fairly safe to say that the contract is not water tight, and if there were the smallest chance of a potential breach, we would absolutely be seeing the EU commission taking the AZ to court (three months ago in fact!)
If it were that easy the EU would not be risking their international reputation with the grubby and unedifying spectacle of strong arming AZ and by extension, the UK into giving up their own vaccines would they!
The EU would sit back smugly and let the EU lawyers make mincemeat of AZ. There would be no need to get their hands dirty with a smear campaign and all the rest that followed.
The legal route is something the EU have completely given up on TheMancunianCandidate because there is no case to answer - and moreover they have moved on to totally trashing the AZ for no reason, which is the most irresponsible action possible, and if I were the CEO we would be pulling out of the EU full stop, and they would get ZERO vaccines.